added stringify_dict

CHANGELOG.md

 # v2.8.4
 
+* added `stringify_dict`

docs/coding/transforms.rst

+Rudimentary data transforms.
+
+stringify_dict
+==============
+
+Make both keys and values of this dict a string, by passing them through stringify function.
+
+.. autofunction:: satella.coding.transforms.stringify_dict

docs/index.rst

@@ -16,6 +16,7 @@ Visit the project's page at GitHub_!
            coding/structures
            coding/concurrent
            coding/sequences
+           coding/transforms
            instrumentation/traceback
            instrumentation/memory
            instrumentation/metrics

satella/__init__.py

-__version__ = '2.8.4_a2'
+__version__ = '2.8.4_a3'

satella/coding/transforms/__init__.py

+import typing as tp
+
+__all__ = ['stringify_dict']
+
+
+def stringify_dict(dct: dict, stringify: tp.Callable[[tp.Any], str]) -> tp.Dict[str, str]:
+    return {stringify(k): stringify(v) for k, v in dct.items()}

tests/test_coding/test_transforms.py

+import unittest
+from satella.coding.transforms import stringify_dict
+
+
+class MyTestCase(unittest.TestCase):
+    def test_stringify_dict(self):
+        dct = {1: 2, 3: 4, 5: 6}
+        self.assertEqual(stringify_dict(dct), {'1': '2', '3': '4', '5': '6'})